Gliederung

Objective: Functional MRI (fMRI) and positron emission tomography (PET) using amino acids are established methods to evaluate neurobiological characteristics of gliomas. The information provided by both fMRI and PET can be used to optimize the extent of cytoreduction and increase the safety of the resection. We describe our first experience with a coregistration of fMRI and PET data with the aim of evaluating the extent of colocalisation between language areas and amino acid uptake in patients with left hemispheric glioma.

Methods: 11 patients (48Â±13 years, 7 male/ 4 female, 1 left-handed) with left hemispheric gliomas (WHO Â° II-IV) were tested for syntactic language production according to the paradigm established by Sach and Kleiser using a 1.5 Tesla scanner. Amino acid uptake in tumor areas was measured using a 32-Ring-PET-Scanner after injection of 200 MBq [18F]-Fluorethyl-L-Tyrosin(FET). FET has been established as a novel tracer with a high sensitivity and specificity for in-vivo detection of gliomas. Image fusion and processing was done using the software PMOD 2.5 and BrainVoyager QX.

Results: As shown previously, a FET lesion/brain ratio of >1.6 detects tumor tissue with a sensitivity of 100% and a specificity of 88%. Using this threshold, we found a median distance between FET-accumulation and fMRI-language activation of 19Â±12 (4-46) mm. Using a threshold of >2.0 for a better visualization of potential hot-spots, we measured a median distance of 14Â±8 (2-29) mm. There was no significant correlation between the measured distance and the WHO grade, integrity of language function, handedness, maximum FET-Uptake or FET-Uptake-Volume.

Conclusions: FET-Uptake and fMRI-language activation appear to be spatiallly distinct (not overlapping) suggesting that areas with a FET lesion/brain ratio of >1.6 can be resected without a functional deficit. Since the distance between language areas and tumor areas were not predictable, our data advise the necessity of an individual evaluation of patients with gliomas in speech-relevant brain areas. Apart from the potential importance of our findings for the surgical planning, the coregistered data can be integrated into the neuronavigation system, making this method a promising tool to increase the safety of cytoreductive glioma surgery.